I really enjoyed this challenge and although it included many steps and was time consuming (I started at 3:30 pm and finished at 8 pm [there was a few steps that required chilling/resting]), it was well worth it.
I began by sauteing the mushrooms, making the herb crepes (the first time I've ever made crepes!), and searing the beef tenderloin steak. Once all that cooled, I began assembling the Beef Wellington.
To begin, I placed two herb crepes (I didn't have any fresh herbs so I just used scallions). I then laid 3-4 pieces of prosciutto down and spread the mushrooms mixture over top. On top of that was the seared tenderloin steak (brushed with Spicy Brown mustard [one of my substitutions, the recipe called for English mustard], it smelled amazing).
Lastly, I laid another crepe on top to ensure that everything was encased (the purpose of the crepe is to prevent the puff pastry or shortcrust pastry from getting soggy).
I then folded up and chilled the crepe, prosciutto, mushroom and tenderloin "log". Once it was properly chilled, I placed the log into the puff pastry sheet (I cheated and didn't make the shortcrust [I blame it on my lack of a food processor]) and folded it up into a package.
And then I chilled it...again! Once chilled and brushed with an egg wash, it baked at 390 degrees for 20 minutes.
I prefer my beef cooked well, so this was underdone for me. I was afraid to overcook the meat, so next time I would sear the meat at a slightly lower temperature and for longer (I think I seared it at medium-high in a cast iron skillet for 3-5 minutes per side).
I really enjoyed this challenge, both the process and the result. I also learned a lot and still feel a sense of accomplishment in successfully cooking a challenging dish!